iPhone 15 Max Pro often does not ring.

My IPhone 15 Max Pro frequently does not ring. I’ve checked to see that the ringer is in, I’ve checked every other possibility, and I can’t figure this out. If I turn it off and back on, it’s fine for a couple of weeks, but then starts up the no ringing thing again. I can be sitting right there next to it, and I get a voicemail because my phone did not ring. It’s infuriating. I’ve never had this problem with an Apple product before.